Multiple reasons...
It could get absorbed into the soil.
It may be absorbed by plants.
It might go through permeable rock and into a groundwater store.
It could also evaporate.
It could, instead of flowing into the ocean, flow into another water store such as a lake or pond.
If it is a large amount of water, humans might dam the area to collect and store the water for long term use.
Hope these answers are alright.
1. Austria Hungry
2. Great Britain
3. Allied Powers
4. Central Powers
